Optical lighting modules of this type are already known. They are capable of emitting, longitudinally forward, a final light beam called “multibeam” or even “pixel beam”. The final light beam projects forward an image of a matrix of elementary light sources. By selectively switching each of the elementary sources on or off, it is possible to create a final light beam specifically lighting certain zones of the road in front of the vehicle, while leaving other zones in darkness.
Such an optical lighting module is used in particular to produce an adaptive lighting function, also called “ADB”, the acronym for “adaptive driving beam”. Such an ADB function is intended to automatically detect a road user likely to be dazzled by a lighting beam emitted in high beam mode by a headlight, and to modify the outline of this lighting beam so as to create a dark zone where the detected user is located while continuing to light the road with a long range on either side of the user. The ADB function offers many advantages: ease of use, better visibility compared to a lighting in low beam mode, greatly reduced risk of dazzle, safer driving etc.
Such an optical module generally comprises a matrix of light sources, usually formed by light-emitting diodes (LEDs), a primary optical element comprising a plurality of light guides and a projection optic. The light-emitting diodes are arranged on a flat printed circuit board which extends in a plane orthogonal to the direction of projection of the final light beam. The light guides of the primary optical element extend overall longitudinally from a light input face to a light output face. The light guides are intended to conform the rays emitted by the light-emitting diodes into a narrower light beam, the output face of each light guide forming a pixel. The output faces of the light guides form a matrix of elementary pixels imaged by the projection optic. Each pixel can be lit selectively by activation or deactivation of each light source.
Such a primary optical element comprises a first row of first light guides intended to form elementary pixels of rectangular form which are intended to light above a cut-off line.
Such a primary optical element also comprises a second row of second light guides intended to form elementary pixels of square form which are intended to light below a cut-off line.
The images of the square pixels thus light the road in proximity to the vehicle, whereas the images of the rectangular pixels light the road to a greater distance.
The images of the rectangular pixels are likely to dazzle road users situated at a short distance from the vehicle. The adaptive lighting consists in detecting such road users and in switching off the light sources forming the pixels likely to dazzle said users while keeping the other light sources switched on to guarantee a good visibility to the driver of the vehicle.
For the optical lighting module to produce a final light beam that is comfortable for the driver, the images of the rectangular pixels vertically overlap the images of the square pixels. It has been found that the comfort of the driver was enhanced when the images of the rectangular pixels extend over more than 5° vertically.
Now, currently, a single light guide does not make it possible to obtain a rectangular pixel of such vertical extent while remaining relatively narrow transversally.
Furthermore, it has also been found that a better visual comfort was obtained when the square pixels have a dimmed bottom edge.
Moreover, a visually comfortable lighting light beam must also light the lower side of the road. Now, even by modifying the form of the light guides arranged at the transverse end of the primary optical element, the pixels produced by the transverse end light guides are not sufficiently wide to sufficiently light the side of the road.